1. Field of the Invention
The present invention relates to a mobile communication radio transceiver designed to operate with multiple modulation modes and multiple frequency bands, wherein the mobile communication radio transceiver operates by switching frequency bands or modulation modes in a plurality of mobile communication systems among which different radio frequency bands and different modulation modes are used. The invention also relates to a receiving mixer circuit for such a mobile communication radio transceiver.
2. Related art of the Invention
FIG. 5 shows an example of a prior art mobile radio transceiver configuration for implementing simultaneously two mobile communication systems that use two different modulation modes with the same frequency band and a mobile communication system that uses either of two modulation modes and two different frequency bands. FIG. 5 shows the block diagram for a multi-mode and multi-band mobile radio transceiver that operates by switching among a mobile communication system A which uses a first radio frequency band and a first modulation mode, a mobile communication system B which uses a second radio frequency band and employs the same first modulation mode as the system A, and a mobile communication system C which uses the same second radio frequency band as the system B and employs a second modulation mode.
In FIG. 5, reference numeral 1 is an antenna, 2 is a frequency select switch for switching between the first and second radio frequency bands, 3 is a first duplexer for the first radio frequency band, 4 is a second duplexer for the second radio frequency band, 5 is a first low-noise amplifier for a first receive frequency band, 6 is a second low-noise amplifier for a second receive frequency band, 7 is a first receiving mixer for the first receive frequency band, 8 is a second receiving mixer for the second receive frequency band, 9 is a first local oscillator for the first radio frequency band, 10 is a second local oscillator for the second radio frequency band, 13 is a first intermediate-frequency filter with a first receive bandwidth corresponding to a first receive intermediate frequency of the first modulation mode, 14 is a second intermediate-frequency filter with a second receive bandwidth corresponding to a second receive intermediate frequency of the second modulation mode, 11 and 12 are select switches for directing the first and second receive intermediate-frequency signals to the corresponding intermediate-frequency filters, 15 is a first demodulator for the first modulation mode, 16 is a second demodulator for the second modulation mode, 17 is a first transmitter for a first transmit frequency band, and 18 is a second transmitter for a second transmit frequency band.
As an example, consider the case where the first transmit frequency range is f1TX=1850 MHz to 1910 MHz, the first receive frequency range is f1RX=1930 MHz to 1990 MHz, the second transmit frequency range is f2TX=824 MHz to 849 MHz, the second receive frequency range is f2RX=869 MHz to 894 MHz, the first receive intermediate frequency is f1IF=180 MHz, the first receive bandwidth is W1=1.23 MHz, the second receive intermediate frequency is f2IF=90 MHz, and the second receive bandwidth is W2=30 KHz.
Referring to FIG. 5, the operation of the mobile communication system A will be described first. A signal on the first radio frequency band transmitted from a base radio transceiver station is received by the antenna 1, and by switching the frequency select switch 2 to the A side, the received signal is fed into the first duplexer 3 where it is separated from the transmitting signal. The separated received signal is amplified by the first low-noise amplifier 5, and converted by the first receiving mixer 7 to the first receive intermediate frequency f1IF. By switching the first select switch 11 to the A side, the output signal of the first receiving mixer 7 is fed into the first intermediate-frequency filter 13. After passing through the first intermediate-frequency filter 13, the signal is input to the first demodulator 15 for demodulation.
Next, the operation of the mobile communication system B will be described. A signal on the second radio frequency band transmitted from a base radio transceiver station is received by the antenna 1, and by switching the frequency select switch 2 to the B side, the received signal is fed into the second duplexer 4 where it is separated from the transmitting signal. The separated received signal is amplified by the second low-noise amplifier 6, and converted by the second receiving mixer 8 to the first receive intermediate frequency f1IF. By switching the first select switch 11 to the B side and the second select switch 12 to the A side, the output signal of the second receiving mixer 8 is fed into the first intermediate-frequency filter 13. After passing through the first intermediate-frequency filter 13, the signal is input to the first demodulator 15 for demodulation.
Finally, the operation of the mobile communication system C will be described. A signal on the second radio frequency band transmitted from a base radio transceiver station is received by the antenna 1, and by switching the frequency select switch 2 to the B side, the received signal is fed into the second duplexer 4 where it is separated from the transmitting signal. The separated received signal is amplified by the second low-noise amplifier 6, and converted by the second receiving mixer 8 to the second receive intermediate frequency f2IF. By switching the second select switch 12 to the B side, the output signal of the second receiving mixer 8 is fed into the second intermediate-frequency filter 14. After passing through the second intermediate-frequency filter 14, the signal is input to the second demodulator 16 for demodulation.
However, since the select switches 11 and 12 are needed to direct the signals output from the receiving mixers to the appropriate intermediate-frequency filters corresponding to the respective modulation modes, the receiving mixer circuit of the above prior art configuration has had the problem that it is disadvantageous in terms of the size and cost of the circuit.